Transceiver suitable for data communications between wearable computers

ABSTRACT

In a transceiver for inducing electric fields based on data to be transmitted in an electric field propagating medium and carrying out transmission and reception of data by using induced electric fields, having a transmission electrode and a transmission circuit, a transmission side switch is provided to disconnect the transmission circuit from the transmission electrode, when the transceiver is not in a transmission state in which the transmission circuit is supplying the transmission data to the transmission electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/255,379, filed Sep. 26, 2002 which is based upon and claimsthe benefit of priority from Japanese Patent Applications JP2001-295121,JP2001-295124, JP2001-295133, JP2001-295135, JP2001-295137,JP2001-295139, all of which were filed on Sep. 26, 2001, and areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transceiver to be used for datacommunications between wearable computers (computers to be worn) forexample, and more particularly to a transceiver for inducing electricfields based on data to be transmitted in an electric field propagatingmedium and carrying out transmission and reception of data by using theinduced electric fields.

The present invention also relates to an electric field detectingoptical device for detecting electric fields based on transmission datawhich are induced in and propagated through an electric fieldpropagating medium such as a living body and converting them intoelectric signals in such a transceiver.

The present invention also relates to a photodetection circuit fordetecting lights with optical characteristics changed by the detectedelectric fields and converting them into electric signals in such anelectric field detecting optical device.

2. Description of the Related Art

Due to the progress in reducing size and improving performance ofportable terminals, the wearable computers are attracting attentions.FIG. 1 shows an exemplary case of using such wearable computers bywearing them on a human body. As shown in FIG. 1, the wearable computers1 are put on arms, shoulders, torso, etc., of the human body throughrespective transceivers 3 and capable of carrying out mutual datatransmission and reception as well as communications with an externallyprovided PC 5 via a cable through transceivers 3 a and 3 b attached attip ends of a hand and a leg.

The transceiver 3 to be used for data communications between thewearable computers 1 in such a way is utilizing the signal detectiontechnique based on the electro-optic method using laser lights andelectro-optic crystals, in which electric fields based on data to betransmitted are induced in a living body which is an electric fieldpropagating medium and data transmission and reception are carried outby using the induced electric fields.

FIG. 2 shows an exemplary configuration of the transceiver 3, which hasan I/O (Input/Output) circuit 101 through which the transceiver 3 isconnected to the wearable computer 1, and a transmission electrode 105and a reception electrode 107 provided in a vicinity of the living body100 through insulation films 106 and 108 respectively. In thistransceiver 3, the electric fields based on the transmission data areinduced in the living body 100 from the transmission electrode 105through the insulation film 106, and the electric fields induced at theother portion of the living body 100 and propagated through the livingbody 100 are received at the reception electrode 107 through theinsulation film 108.

More specifically, in this transceiver 3, when the transmission datafrom the wearable computer 1 are received through the I/O circuit 101,these transmission data are supplied to a transmission circuit 103 afteradjusting their level at a level adjustment circuit 102. Thetransmission circuit 103 supplies the level adjusted transmission datato the transmission electrode 105, and the electric fields based on thetransmission data are induced in the living body 100 from thetransmission electrode 105 through the insulation film 100, such thatthe induced electric fields are propagated to the transceiver 3 providedat the other portion of the living body 100.

On the other hand, when the electric fields induced at the other portionof the living body 100 and propagated through the living body 100 arereceived at the reception electrode 107 provided in a vicinity of theliving body 100 through the insulation film 108, the received electricfields are coupled to an electric field detecting optical unit 110,converted into electric signals by the electro-optic method using laserlight and electro-optic element at the electric field detecting opticalunit 110, and supplied to a signal processing circuit 109.

In further detail, as shown in FIG. 3, the electric fields are coupledto an electro-optic crystal 131 onto which the laser light from a laserlight source 133 is injected, so as to change the polarization state ofthe laser light. The changes of the polarization state of the laserlight are then detected and converted into electric signals by apolarization detecting optical system 135, and supplied to the signalprocessing circuit 109. Here, the laser light source 133 is operated bycurrents supplied from a current source 137.

The signal processing circuit 109 applies signal processings such as lownoise amplification, noise removal, waveform shaping, etc., with respectto the electric signals from the electric field detecting optical unit110 or the polarization detecting optical system 135, and supplies themto the wearable computer 1 through the I/O circuit 101.

In the above described conventional transceiver, the transmissioncircuit 103 and the level adjustment circuit 102 are always connected tothe transmission electrode 105, so that while the reception electrode107 are in a process of receiving the electric fields based on thetransmission data from the other portion of the living body 100, thenoises from a power source or the like are supplied to the transmissionelectrode 105 from the transmission circuit 103 and the level adjustmentcircuit 102, and the electric fields due to these noises are induced inthe living body 100 from the transmission electrode 105 and propagatednot only to the same transceiver 3 but also to the reception electrode107 of the other transceiver 3 as well, and this can be a cause of theoperation error.

Also, in the above described conventional transceiver, after the leveladjustment of the transmission data received from the wearable computer1, the electric fields are induced in the living body 100 from thetransmission circuit 103 through the transmission electrode 105 and theinsulation film 106 and propagated through the living body 100, andthese electric fields are received through the insulation film 108 andthe reception electrode 107 at the other portion of the living body 100.However, the electric fields induced in and propagated through theliving body 100 in this manner have weak levels, so that they have apoor S/N ratio, a high probability for causing the operation error, anda poor reliability.

Also, the above described transceiver requires the power consumption tobe as small as possible because it is to be used by being put on theliving body 100 along with the wearable computer 1. On the other hand,there is no need for the laser light source 133 to be operated all thetimes. For example, there is no need to operate the laser light source133 at a time of transmission at which the electric fields are not to bereceived. However, in the above described conventional transceiver, thelaser light source 133 is always operated to generate the laser light sothat it is always possible to detect the electric fields induced in andpropagated through the living body 100. Consequently, there has beenwasteful power consumption as the laser light source 133 is operatedeven in a state where there is no need to operate the laser light source133 such as the transmission state in particular.

Also, for the sake of the practical realization of such a wearablecomputer, the scheme for data communications between the wearablecomputers is very important, and the conventionally available scheme fordata communications between the wearable computers include a scheme forcarrying out wired communications by connecting the transceiversconnected to the wearable computers by a data line and a ground line, ascheme for carrying out radio communications by connecting thetransceivers by radio, and a scheme for carrying out data transmissionand reception by using the living body as a signal line and the Earthground with which the living body is in contact as a ground line (seePAN: Personal Area Network, IBM SYSTEMS JOURNAL, Vol. 35, Nos. 3 & 4,pp. 609-617, 1996).

However, the wired communication scheme requires to connect thetransceivers by two cable lines, and in the case of carrying out datatransmission and reception between distant wearable computers or among aplurality of wearable computers, it becomes necessary to arrange manycable lines all over the body so that it is not practical.

Also, the radio communication scheme has a possibility of crosstalkingwith the other systems existing nearby depending on the radiofrequencies and powers.

Also, the wearable computers are expected to be mostly put on the upperhalf body in general, but the communication scheme utilizing the livingbody as a signal path has a practical problem in this regard in that thecommunications become impossible when the transceiver of the wearablecomputer is arranged far from the Earth ground such as at the head forexample.

FIG. 4 shows another exemplary configuration of the transceiver 3, whichhas the I/O circuit 101 through which the transceiver 3 is connected tothe wearable computer 1, and the transmission electrode 105 and thereception electrode 107 provided in a vicinity of the living body 100through the insulation films 106 and 108 respectively, similarly as inthe transceiver of FIGS. 2 and 3.

More specifically, in this transceiver 3, when the transmission datafrom the wearable computer 1 are received through the I/O circuit 101,these transmission data are supplied to a transmission circuit 103 afteradjusting their level at a level adjustment circuit 102. Thetransmission circuit 103 supplies the level adjusted transmission datato the transmission electrode 105, and the electric fields based on thetransmission data are induced in the living body 100 from thetransmission electrode 105 through the insulation film 100, such thatthe induced electric fields are propagated to the transceiver 3 providedat the other portion of the living body 100.

On the other hand, when the electric fields induced at the other portionof the living body 100 and propagated through the living body 100 arereceived at the reception electrode 107 provided in a vicinity of theliving body 100 through the insulation film 108, the received electricfields are coupled to an electric field detecting optical unit 110,converted into intensity changes of lights composed of P-polarizationcomponents and S-polarization components by the electro-optic methodusing laser light and electro-optic element at the electric fielddetecting optical unit 110, and supplied to a photodetection circuit120.

The photodetection circuit 120 converts the light signals composed ofP-polarization components and the S-polarization components from theelectric field detecting optical unit 110 into electric signals. Theseelectric signals are then subjected to a noise removal by a band-passfilter 132 and a waveform shaping by a waveform shaping circuit 134, andsupplied as received data to the wearable computer 1 through the I/Ocircuit 101.

The photodetection circuit 120 is formed by a circuit called a balanceddetection and single amplification type circuit as shown in FIG. 5, inwhich a midpoint of first and second photodiodes 91 and 93 that areconnected in series between bias voltage sources (+V, −V) is groundedthrough a load resistor 95 as well as connected to an input of anamplifier 97.

The first and second photodiodes 91 and 93 constituting thisconventional photodetection circuit 120 are playing the role of adifferential amplifier, and when the light signals with intensitychanges in opposite phases composed of P-polarization components and theS-polarization components from the electric field detecting optical unit110 are detected, the first and second photodiodes 91 and 93 producecurrents generated in response to respective light signals such thatthey are added together at the load resistor 95 to double the currents,and a voltage corresponding to these doubled currents is generated atboth ends of the load resistor 95 and supplied as an input voltage tothe amplifier 97.

Now, the laser lights generated at the electric field detecting opticalunit 110 utilizing the electro-optic method contain noises generatedfrom the laser diode itself or the power source in general. The lightsignals injected into the first and second photodiodes 91 and 93 of thephotodetection circuit 120 from the electric field detecting opticalunit 110 that uses such noise mixed laser lights will also containnoises, so that there is a need to remove these noises. In thephotodetection circuit of FIG. 5, such noises mixed in the laser lightshave the same phase and same level so that they are removed by thebalanced detection made by the first and second photodiodes 91 and 93and the load resistor 95, and they will not be entered into theamplifier 97.

However, the noises mixed at the photodetection circuit as shown in FIG.5 include not only the noises mixed in the laser lights but also noisesmixed into output current signals of the photodiodes via a metalliccasing that covers outer sides of the photodiodes 91 and 93, forexample. Such noises do not necessarily have the same phase and samelevel unlike the noises mixed in the laser lights, and the noise levelsmay vary depending on the positional relationship between the noisesource and the photodiodes 91 and 93 or on the way in which the noisesare mixed, so that they cannot be removed by the conventionalphotodetection circuit such as that shown in FIG. 5.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide atransceiver for enabling bidirectional communications by preventingpropagation of noises from internal circuits to the transmissionelectrode, by separating the transmission electrode from the internalcircuits while not in the transmission state.

It is another object of the present invention to provide a transceiverin which the S/N ratio is improved by modulating the electric fieldsinduced in and propagated through the electric field propagating mediumby utilizing the resonant frequency due to the inverse piezo-electriceffect of the electro-optic element.

It is another object of the present invention to provide a transceivercapable of reducing the power consumption by controlling the operationof the light source according to the operation state of the transceiver.

It is another object of the present invention to provide an electricfield detecting optical device to be used for carrying out the datacommunications using electric fields properly, which is suitable for usein the transceiver for the wearable computer, which does not require anycable lines, which is not radio, and which basically does not depend onthe Earth ground.

It is another object of the present invention to provide aphotodetection circuit capable of properly removing not only the noisesmixed in the laser lights but also the other noises that are mixed atdifferent levels.

According to one aspect of the present invention there is provided atransceiver for inducing electric fields based on data to be transmittedin an electric field propagating medium and carrying out transmissionand reception of data by using induced electric fields, comprising: atransmission electrode configured to induce the electric fields based onthe data to be transmitted in the electric field propagating medium; atransmission circuit configured to supply transmission data for causingthe transmission electrode to induce the electric fields based on thedata to be transmitted in the electric field propagating medium, to thetransmission electrode; and a transmission side switch configured todisconnect the transmission circuit from the transmission electrode,when the transceiver is not in a transmission state in which thetransmission circuit is supplying the transmission data to thetransmission electrode.

According to another aspect of the present invention there is provided atransceiver for inducing electric fields based on data to be transmittedin an electric field propagating medium and carrying out transmissionand reception of data by using induced electric fields, comprising: atransmission electrode configured to induce the electric fields based onthe data to be transmitted in the electric field propagating medium; atransmission circuit configured to supply transmission data for causingthe transmission electrode to induce the electric fields based on thedata to be transmitted in the electric field propagating medium, to thetransmission electrode; a reception electrode configured to receiveelectric fields induced in and propagated through the electric fieldpropagating medium; an electric field detection unit configured todetect received electric fields as received by the reception electrode,and convert the received electric fields into electric signals bycausing a resonance in an electro-optic element by using the receivedelectric fields; a modulation circuit configured to modulate thetransmission data by using resonant frequencies of the electro-opticelement as modulation frequencies, and supply modulated transmissiondata to the transmission circuit; and a demodulation circuit configuredto demodulate the electric signals from the electric field detectionunit.

According to another aspect of the present invention there is provided atransceiver for inducing electric fields based on data to be transmittedin an electric field propagating medium and carrying out transmissionand reception of data by using induced electric fields, comprising: alight source configured to generate lights; an electric field detectionunit configured to detect electric fields induced in and propagatedthrough the electric field propagating medium by using lights from thelight source, convert the electric fields into electric signals, andoutput the electric signals; and a control unit configured to control anoperation of the light source according to an operation state of thetransceiver.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an exemplary case of using wearablecomputers by putting them on a human body through transceivers.

FIG. 2 is a block diagram showing one exemplary configuration of aconventional transceiver for a wearable computer.

FIG. 3 is a block diagram showing another exemplary configuration of aconventional transceiver for a wearable computer.

FIG. 4 is a block diagram showing another exemplary configuration of aconventional transceiver for a wearable computer.

FIG. 5 is a circuit diagram showing an exemplary configuration of aconventional photodetection circuit to be used in the transceiver ofFIG. 4.

FIG. 6 is a block diagram showing one exemplary configuration of atransceiver according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing another exemplary configuration of atransceiver according to the first embodiment of the present invention.

FIG. 8 is a block diagram showing one exemplary configuration of atransceiver according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing another exemplary configuration of atransceiver according to the second embodiment of the present invention.

FIG. 10 is a block diagram showing one exemplary configuration of atransceiver according to the third embodiment of the present invention.

FIG. 11 is a block diagram showing another exemplary configuration of atransceiver according to the third embodiment of the present invention.

FIG. 12 is a graph of a laser optical power versus time for explainingone exemplary operation of the transceiver of FIG. 10 or FIG. 11.

FIG. 13 is a graph of a laser optical power versus time for explaininganother exemplary operation of the transceiver of FIG. 10 or FIG. 11.

FIG. 14 is a graph of a laser optical power versus time for explaininganother exemplary operation of the transceiver of FIG. 10 or FIG. 11.

FIG. 15 is a diagram showing a first exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fourth embodiment of the present invention.

FIG. 16 is a diagram showing a second exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fourth embodiment of the present invention.

FIG. 17 is a diagram showing a third exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fourth embodiment of the present invention.

FIG. 18 is a diagram showing a fourth exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fourth embodiment of the present invention.

FIG. 19 is a diagram showing a fifth exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fourth embodiment of the present invention.

FIG. 20 is a diagram showing a first exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 21 is a diagram showing a second exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 22 is a diagram showing a third exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 23 is a diagram showing a fourth exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 24 is a diagram showing a fifth exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 25 is a diagram showing a sixth exemplary configuration of anelectric field detecting optical device to be used in a transceiveraccording to the fifth embodiment of the present invention.

FIG. 26 is a circuit diagram showing a first exemplary configuration ofa photodetection circuit to be used in an electric field detectingoptical device of a transceiver according to the sixth embodiment of thepresent invention.

FIG. 27 is a circuit diagram showing a second exemplary configuration ofa photodetection circuit to be used in an electric field detectingoptical device of a transceiver according to the sixth embodiment of thepresent invention.

FIG. 28 is a circuit diagram showing a third exemplary configuration ofa photodetection circuit to be used in an electric field detectingoptical device of a transceiver according to the sixth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 6 and FIG. 7, the first embodiment of atransceiver according to the present invention will be described indetail.

FIG. 6 shows a circuit configuration of a transceiver according to thefirst embodiment of the present invention. The transceiver of FIG. 6differs from the conventional transceiver of FIG. 2 in that a firstanalog switch 104 is provided between the transmission circuit 103 andthe transmission electrode 105, a second analog switch 113 is providedbetween the signal processing circuit 109 and the I/O circuit 101, and amonostable multivibrator 111, which is a monostable circuit thatfunctions as a signal output unit that is operated by being triggered bythe transmission data outputted from the I/O circuit 101, is providedsuch that its output signal controls the first analog switch 104, thesecond analog switch 113, the transmission circuit 103 and the electricfield detecting optical unit 110. The rest of the configuration and theoperation of the transceiver of FIG. 6 are the same as those of FIG. 2,and the same reference numerals are given to the corresponding elements.

Note that the configuration of FIG. 6 can be modified to that shown inFIG. 7, where the transmission electrode 105 and the reception electrode107 of FIG. 6 are integrally provided as a transmission and receptionelectrode 105′ in FIG. 7, and the insulation films 106 and 108 of FIG. 6are integrally provided as an insulation film 106′ in FIG. 7.

The monostable multivibrator 111 is triggered by detecting a start ofdata packets that are the transmission data supplied from the wearablecomputer 1 through the I/O circuit 101, and generates a first outputsignal of a first level (high level, for example) for a prescribedperiod of time since the start time of the data packets, such as aprescribed period of time corresponding to the duration of the datapackets during which the data packets are outputted, or generates asecond output signal of a second level (low level, for example) forremaining periods of time, i.e., periods at which the data packets arenot outputted. The monostable multivibrator 111 supplies these first andsecond output signals to the first analog switch 104, the second analogswitch 113, the transmission unit 103 and the electric field detectingoptical unit 110. Namely, the first output signal to be outputted for aprescribed period of time from the monostable multivibrator 111indicates that the transceiver 3 is in the transmission state, and thesecond output signal from the monostable multivibrator 111 indicatesthat the transceiver 3 is not in the transmission state but in a statecapable of receiving data from the other transceivers 3.

When the first output signal from the monostable multivibrator 111 issupplied, the first analog switch 104 is turned ON, such that thetransmission electrode 105 and the transmission circuit 103 areconnected, the data packets constituting the transmission data suppliedthrough the transmission circuit 103 are supplied to the transmissionelectrode 105, and the electric fields based on the transmission dataare induced in the living body 100 through the transmission electrode105 and propagated to the other transceiver 3 provided at the otherportion of the living body 100.

Also, when the second output signal from the monostable multivibrator111 is supplied, the first analog switch 104 is turned OFF, such thatthe transmission electrode 105 and the transmission circuit 103 areseparated, i.e., the signal path between the transmission electrode 105and the transmission circuit 103 is disconnected, and the noises fromthe power source or the like will not be supplied to the transmissionelectrode 105 through the transmission circuit 103 and the leveladjustment circuit 102. As a result, the first analog switch 104 isturned OFF while the transceiver 3 is in a state of not outputting thetransmission data so that the electric fields due to the noises will notbe induced in the living body 100 and therefore it is possible toprevent the reception electrode 107 to cause the operation error byreceiving the noise electric fields.

On the other hand, when the first output signal from the monostablemultivibrator 111 is supplied, the second analog switch 113 is turnedOFF, such that the signal processing circuit 109 and the I/O circuit 101are separated, i.e., the signal path between the signal processingcircuit 109 and the I/O circuit 101 is disconnected, and the noises dueto the noise electric fields received by the reception electrode 107will not be supplied to the I/O circuit 101 through the electric fielddetecting optical unit 110 and the signal processing circuit 109 tocause the operation error.

Note that, in this embodiment, the second analog switch 113 is connectedbetween the signal processing circuit 109 and the I/O circuit 101 so asto disconnect the signal path between them, but it is not necessarilylimited to this case, and it is also possible to provide the secondanalog switch 113 between the electric field detecting optical unit 110and the signal processing circuit 109 so as to disconnect the signalpath between them. In essence, it suffices to disconnect the propagationpath of the received signals on the circuit section subsequent to theelectric field detecting optical unit 110.

Also, when the second output signal from the monostable multivibrator111 is supplied, the second analog switch 113 is turned ON, such thatthe signal processing circuit 109 and the I/O circuit 101 are connected,and the signals due to the electric fields received by the receptionelectrode 107 will be supplied to the I/O circuit 101 through theelectric field detecting optical unit 110 and the signal processingcircuit 109.

As already mentioned above, the electric field detecting optical unit110 utilizes the signal detection technique based on the electro-opticmethod using laser lights and the electro-optic crystals, and internallyhas a laser diode (not shown). In this embodiment, when the transceiver3 is not in the reception state, there is no need to operate theelectric field detecting optical unit 110 and therefore there is no needto operate the laser diode, so that the laser diode provided inside theelectric field detecting optical unit 110 is controlled to be operatedonly during the reception state and not operated during the transmissionstate according to the output signals from the monostable multivibrator111, so as to reduce the power consumption.

Namely, when the first output signal from the monostable multivibrator111 is supplied, the electric field detecting optical unit 110 turns thelaser diode OFF, and when the second output signal from the monostablemultivibrator 111 is supplied, the electric field detecting optical unit110 turns the laser diode ON.

Note that, in the above description, only the laser diode is turnedON/OFF, but it is also possible to apply this ON/OFF control to theentire electric field detecting optical unit 110 including the laserdiode. Namely, it is also possible to control such that, when the firstoutput signal from the monostable multivibrator 111 is supplied, theentire electric field detecting optical unit 110 is turned OFF, and whenthe second output signal from the monostable multivibrator 111 issupplied, the entire electric field detecting optical unit 110 is turnedON. In this case, it is possible to reduce the power consumptionfurther.

The first and second output signals from the monostable multivibrator111 are also supplied to the transmission circuit 103, and thetransmission circuit 103 has a built-in switch that is turned ON/OFF bythe first and second output signals from the monostable multivibrator111 such that, when the first output signal from the monostablemultivibrator 111 is supplied, this switch is turned ON and the power tooperate the transmission circuit 103 is supplied, and when the secondoutput signal from the monostable multivibrator 111 is supplied, thisswitch is turned OFF and the power supply is stopped so that theoperation of the transmission circuit 103 is stopped, for example. As aresult, it is possible to reduce the power consumption by thetransmission circuit 103 while the transceiver is in a state other thanthe transmission state, i.e., the reception state or the receptionwaiting state.

Note that, in the above description, the first analog switch 104 isturned ON to connect the transmission circuit 103 to the transmissionelectrode 105 by the first output signal from the monostablemultivibrator 111 which is outputted for a prescribed period of timesince the start time of the data packets, and turned OFF to separate thetransmission circuit 103 from the transmission electrode 105 during theother periods at which the second output signal is outputted from themonostable multivibrator 111. In this regard, in essence, it suffices toturn the first analog switch 104 ON to connected the transmissioncircuit 103 to the transmission electrode 105 only while the transceiver3 is in the transmission state, and to turn the first analog switch 104OFF to separate the transmission circuit 103 from the transmissionelectrode 105 while the transceiver 3 is not in the transmission statesuch that the noises from the level adjustment circuit 102 and thetransmission circuit 103 will not induce the noise electric fields inthe living body 100.

Similarly, in the above description, the second analog switch 113 isturned OFF to separate the signal processing circuit 109 from the I/Ocircuit 101 when the first output signal from the monostablemultivibrator 111 is supplied, and turned ON to connect the signalprocessing circuit 109 to the I/O circuit 101 during the other periodsat which the second output signal is outputted from the monostablemultivibrator 111. In this regard, in essence, it suffices to turn thesecond analog switch OFF to separate the signal processing circuit 109from the I/O circuit 101 only while the transceiver 3 is in thetransmission state, and to turn the second analog switch 113 ON toconnect the signal processing circuit 109 to the I/O circuit 101 whilethe transceiver 3 is not in the transmission state such that the datadue to the electric fields received by the reception electrode 107 canbe propagated to the I/O circuit 101.

As described, according to the first embodiment, the transmissioncircuit is separated from the transmission electrode by the first analogswitch when the transceiver is not in the transmission state, so that itis possible to prevent the noises of the power source or the like fromthe transmission circuit to induce the noise electric fields in theelectric field propagating medium and being propagated to the receivingside in the reception state or the reception waiting state, andtherefore it becomes possible to carry out the bidirectionalcommunication operation properly without the operation error.

Also, according to the first embodiment, the electric field detectingoptical unit is separated from the signal processing circuit or thesignal processing circuit is separated from the circuit subsequent tothe signal processing circuit by the second analog switch when thetransceiver is in the transmission state, so that it is possible toprevent the transmission data to be propagated to the receiving side ofthe same transceiver, and therefore it becomes possible to carry out thebidirectional communication operation properly.

Also, according to the first embodiment, the transmission is madepossible by turning the transmission path ON for a prescribed period oftime since the start of the data packets, and the transmission path isturned OFF for the other periods, so that it is possible to identify thetransmission state accurately and easily according to the data packets,and the signal path of the transmission circuit is turned OFF in thereception state or the reception waiting state, so that it is possibleto prevent the noises of the power source or the like to induce thenoise electric fields in the electric field propagating medium and beingpropagated to the receiving side, and therefore it becomes possible tocarry out the bidirectional communication operation properly without theoperation error.

Also, according to the first embodiment, the transmission circuit isoperated by supplying the power while the first output signal isoutputted from the monostable multivibrator, and the operation of thetransmission circuit is stopped by stopping the power supply while thesecond output signal is outputted from the monostable multivibrator, sothat it is possible to prevent the noises of the power source or thelike from the transmission circuit to induce the noise electric fieldsin the electric field propagating medium and being propagated to thereceiving side in the reception state or the reception waiting state,and therefore it becomes possible to carry out the proper operation, andit becomes possible to reduce the power consumption by the transmissioncircuit in the reception state or the reception waiting state.

Also, according to the first embodiment, the operation of the electricfield detecting optical unit is stopped by stopping the power supplywhile the first output signal is outputted from the monostablemultivibrator, and the electric field detecting optical unit is operatedby supplying the power while the second output signal is outputted fromthe monostable multivibrator, so that it is possible to prevent thetransmission data to be propagated to the receiving side of the sametransceiver, and therefore it becomes possible to carry out the properoperation, and it becomes possible to reduce the power consumption bythe electric field detecting optical unit in the transmission state.

Referring now to FIG. 8 and FIG. 9, the second embodiment of atransceiver according to the present invention will be described indetail.

FIG. 8 shows a circuit configuration of a transceiver according to thesecond embodiment of the present invention. The transceiver of FIG. 8differs from the conventional transceiver of FIG. 2 in that a modulationcircuit 121 is provided between the level adjustment circuit 102 and thetransmission circuit 103, and a demodulation circuit 123 is providedbetween the electric field detecting optical unit 110 and the signalprocessing circuit 109. The rest of the configuration and the operationof the transceiver of FIG. 8 are the same as those of FIG. 2, and thesame reference numerals are given to the corresponding elements.

Note that the configuration of FIG. 8 can be modified to that shown inFIG. 9, where the transmission electrode 105 and the reception electrode107 of FIG. 8 are integrally provided as a transmission and receptionelectrode 105′ in FIG. 9, and the insulation films 106 and 108 of FIG. 8are integrally provided as an insulation film 106′ in FIG. 9.

In the transceiver 3 of FIG. 8, the electro-optic element utilized forthe electro-optic method of the electric field detecting optical unit110 has the electro-optic characteristic such that, when it is coupledwith the electric field, its birefringence changes due to the Pockelseffect which is the primary electro-optic effect, and when the laserlight is injected in this state, it changes the polarization state ofthe laser light. In addition, the electro-optic element also exhibitsthe phenomenon called inverse piezo-electric effect such that when it iscoupled with the electric field, its crystal is physically distorted.The polarization of the laser light is also changed by this distortiondue to the inverse piezo-electric effect (the photoelasticity effect).

Also, when the electric field to be coupled to the electro-optic elementis changed at some frequency, the physical distortion of theelectro-optic element also changed at that frequency, and when thischange resonates with a distance between opposite faces of theelectro-optic element, the polarization change of the laser lightbecomes extremely large.

The transceiver 3 of FIG. 8 utilizes a resonant frequency that causesthis resonance effect for the purpose of the modulation of thetransmission data, so as to improve the S/N ratio. Note that theelectro-optic element has a plurality of resonant frequencies, so thatfor the purpose of the modulation, arbitrary two resonant frequenciescorresponding to the high level and the low level of the transmissiondata are utilized as the digital modulation frequencies, and these twodigital modulation frequencies are supplied to the modulation circuit121 and the demodulation circuit 123.

The modulation circuit 121 modulates the transmission data from thelevel adjustment circuit 102 by using these two digital modulationfrequencies and supplies the modulated transmission data to thetransmission circuit 103. The transmission circuit 103 supplies themodulated transmission data from the modulation circuit 121 to thetransmission electrode 105. The transmission electrode 105 induces theelectric fields corresponding to the modulated transmission data in theliving body 100 through the insulation film 106.

The electric fields induced in the living body 100 in this manner arethen propagated to the transceiver 3 provided at the other portion ofthe living body 100. At this transceiver 3, the reception electrode 107receives the electric fields through the insulation film 108 and couplesthem to the electric field detecting optical unit 110.

In the electric field detecting optical unit 110, the electro-opticelement is resonated by the coupled electric fields to increase thepolarization changes of the laser light, and the electric signalsmodulated at the two digital modulation frequencies are supplied to thedemodulation circuit 123.

The demodulation circuit 123 demodulates the electric signals suppliedfrom the electric field detecting optical unit 110 by using the twodigital modulation frequencies, and supplies them to the signalprocessing circuit 109. The signal processing circuit 109 applies signalprocessings such as low noise amplification, noise removal, waveformshaping, etc., with respect to the demodulated electric signals from thedemodulation circuit 123, and supplies them to the wearable computer 1through the I/O circuit 101.

As described, according to the second embodiment, the transmission dataare modulated by the resonant frequencies of the electro-optic element,and the modulated transmission data are propagated by inducing theelectric fields in the electric field propagating medium from thetransmission electrode. Then, the propagated electric fields arereceived by the reception electrode, the electro-optic element of theelectric field detecting optical unit is resonated to convert them intoelectric signals, and these electric signals are demodulated.Consequently, the polarization changes become extremely large due to theresonance of the electro-optic element, and the transmission andreception are carried out by using the modulated electric signals, sothat the S/N ratio can be improved, the operation error can beeliminated, and the reliability can be improved.

Also, according to the second embodiment, the transmission data aremodulated by using arbitrary two resonant frequencies as digitalmodulation frequencies corresponding to the high level and the low levelof the transmission data, so that the S/N radio can be improved, theoperation error can be eliminated, and the reliability can be improved.

Referring now to FIG. 10 to FIG. 14, the third embodiment of atransceiver according to the present invention will be described indetail.

FIG. 10 shows a circuit configuration of a transceiver according to thethird embodiment of the present invention. The transceiver of FIG. 10differs from the conventional transceiver of FIG. 3 in that a controlcircuit 141 is provided and the current source 137 for operating thelaser light source 133 is controlled by this control circuit 141. Therest of the configuration and the operation of the transceiver of FIG.10 are the same as those of FIG. 3, and the same reference numerals aregiven to the corresponding elements.

Note that the configuration of FIG. 10 can be modified to that shown inFIG. 11, where the transmission electrode 105 and the receptionelectrode 107 of FIG. 10 are integrally provided as a transmission andreception electrode 105′ in FIG. 11, and the insulation films 106 and108 of FIG. 10 are integrally provided as an insulation film 106′ inFIG. 11.

The control circuit 141 monitors the operation state of the transceiver3, controls the current source 137 that supplies currents to the laserlight source 133 according to the operation state, and imposes thelimitation such as that in which the operation of the laser light source133 is stopped in the transmission state in which the laser light isunnecessary, for example, so as to reduce the power consumption of thetransceiver 3.

More specifically, the transceiver 3 has the transmission state, thereception state, the waiting state, and the communicating mode state,and in this embodiment, as shown in a graph of the laser optical powerversus time shown in FIG. 12, the control circuit 141 controls thecurrent source 137 to supply the currents to the laser light source 133only when the transceiver 3 is in the reception state, i.e., wheneverthe control unit 141 judges that the transceiver 3 is in the receptionstate during either one of the waiting state and the communicating modestate, such that the laser light source 133 generates the stationarylevel or full state laser light, so that the electric fields from theother transceivers can be received. Note that, in FIG. 12, the receptionstate and the transmission state are indicated by “receive” and“transmit” described over graphs representing the laser optical powers.

Then, the control circuit 141 controls the current source 137 not tosupply the currents to the laser light source 133 in the states otherthan the reception state, such that the output of the laser light fromthe laser light source 133 is stopped and the power consumption isreduced.

FIG. 13 shows another graph of the laser optical power versus time forexplaining another exemplary operation of the transceiver 3 according tothis third embodiment of the present invention.

In this case, the configuration of the transceiver 3 is the same as thatshown in FIG. 10, but the control by the control circuit 141 isdifferent.

Namely, in this case, when the control circuit 141 judges that thetransceiver 3 is in the reception state, the control circuit 141controls the current source 137 to supply the currents of the stationarylevel to the laser light source 133 during this reception state, suchthat the laser light source 133 generates the stationary level of fullstate laser light, so that the electric fields from the othertransceivers can be received, similarly as in the case of FIG. 12.

On the other hand, in the case of the states other than the receptionstate, if the laser light output from the laser light source 133 isstopped as in the case of FIG. 12, there can be cases where the laserlight source 133 cannot be re-activated quickly when an attempt is madeto operate the laser light source 133 from this stopped state.

For this reason, in the case shown in FIG. 13, the control circuit 141controls the current source 137 to supply the currents at a prescribedlow level that is lower than the stationary level to the laser lightsource 133 in the states other than the reception state, such that thelaser light source 133 is not completely turned OFF and maintained atsome small power of the warming up level even in the states other thanthe reception state. In this way, even when the state changes to thereception state from this state, the laser light source 133 can bere-activated quickly to generate the stationary level or full statelaser light when the stationary level currents are supplied. Note that,in FIG. 13, the reception state and the transmission state are indicatedby “receive” and “transmit” described over graphs representing the laseroptical powers, similarly as FIG. 12.

Note that it suffices for the currents of the prescribed low level to bethe minimum necessary currents such that the laser light source 133 canbe re-activated quickly to generate the stationary level or full statelaser light when the stationary level currents for enabling thegeneration of the stationary level or full state laser light aresupplied in the state where the currents of the prescribed low level aresupplied.

By maintaining the laser light source 133 at some small power withoutturning it OFF completely by supplying the low level currents to thelaser light source 133 in the states other than the reception state asdescribed above, the power consumption will be increased slightlycompared with the case of FIG. 12, but the re-activation of the laserlight source 133 can be made quick, the operation error in the receptionstate can be eliminated, and the reliability can be improved.

FIG. 14 shows another graph of the laser optical power versus time forexplaining another exemplary operation of the transceiver 3 according tothis third embodiment of the present invention.

In this case, the configuration of the transceiver 3 is the same as thatshown in FIG. 10, but the control by the control circuit 141 isdifferent.

Namely, in this case, the control circuit 141 controls the currentsource 137 to supply the stationary level currents to the laser lightsource 133 such that the laser light source 133 generates the stationarylevel or full state laser light, both in the reception state and thetransmission state during the communicating mode state when thetransceiver 3 is in the communicating mode state, as indicated in thesecond half of FIG. 14, so as to improve the reliability of thetransmission and reception in the case where the transmission and thereception are alternated repeatedly in succession as in the case of thecommunicating mode state.

Also, besides the communicating mode state, the control circuit 141controls the current source 137 to supply the stationary level currentsto the laser light source 133 such that the laser light source 133generates the stationary level or full state laser light in thereception state, i.e., the reception state during the waiting state, asindicated in the first half of FIG. 14, similarly as in the case of FIG.13. Then, the control circuit 141 controls the current source 137 tosupply the currents at a prescribed low level that is lower than thestationary level to the laser light source 133 in the states other thanthe reception state during the waiting state, such that the laser lightsource 133 is not completely turned OFF and maintained at some smallpower of the warming up level even in the states other than thereception state. In this way, even when the state changes to thereception state from this state, the laser light source 133 can bere-activated quickly to generate the stationary level or full statelaser light when the stationary level currents are supplied. Note that,in FIG. 14, the reception state and the transmission state are indicatedby “receive” and “transmit” described over graphs representing the laseroptical powers, similarly as FIG. 13.

Note that the above description is directed to the case of using thelaser light source 133, but this embodiment is not necessarily limitedto the case of using the laser light source.

As described, according to this embodiment, the operation of the lightsource is controlled according to the operation state of thetransceiver, so that it is possible to reduce the power consumption bystopping the operation of the light source when the transceiver is inthe transmission state that does not require the light source, forexample.

Also, according to this embodiment, the light is generated from thelight source by supplying the currents to the light source only when thetransceiver is in the reception state, so that it is possible to reducethe power consumption as the currents are not supplied to the lightsource in the states other than the reception state.

Also, according to this embodiment, the light is generated from thelight source by supplying the currents to the light source when thetransceiver is in the reception state, and the low level currents aresupplied to the light source in the states other than the receptionstate to maintain the light source at some small power, such that there-activation of the light source can be made quick, the operation errorin the reception state is eliminated, and the reliability can beimproved.

Also, according to this embodiment, the light is generated from thelight source by supplying the currents to the light source when thetransceiver is in the reception state or in the communicating modestate, and the low level currents are supplied to the light source inthe other states, so as to improve the reliability of the transmissionand reception in the case where the transmission and the reception arealternated repeatedly in succession as in the case of the communicatingmode state. Also, the low level currents are supplied to the lightsource in the other states to maintain the light source at some smallpower, such that the re-activation of the light source can be madequick, the operation error in the reception state is eliminated, and thereliability can be improved.

Referring now to FIG. 15 to FIG. 19, the fourth embodiment of thepresent invention related to the electric field detecting optical devicewill be described in detail.

FIG. 15 shows a first exemplary configuration of the electric fielddetecting optical device according to this embodiment.

The electric field detecting optical device 11 of FIG. 15 is to be usedas the electric field detecting optical unit 110 in the transceiver 3 ofthe first to third embodiments described above, in the case of puttingthe wearable computer 1 on the living body 100 which is an electricfield propagating medium and enabling the data communications with theother wearable computers and data communication devices.

The electric field detecting optical device 11 of FIG. 15 detects theelectric fields by the electro-optic method using laser lights andelectro-optic crystals, and has a laser diode 21 constituting a laserlight source and an electro-optic element 23 in a form of anelectro-optic crystal. Note that the electro-optic element 23 of thisembodiment is sensitive only to electric fields coupled in a directionperpendicular to a propagating direction of the laser light from thelaser diode 21, where the optical characteristic, i.e., thebirefringence, is changed by the electric field strength and thepolarization of the laser light is changed by the change of thebirefringence.

Note also that the laser light outputted from the laser diode 21 is usedin this embodiment, but it is not necessarily limited to the laser lightand it suffices to be a single wavelength light, so that it is alsopossible to use the light outputted from a light emitting diode (LED),for example. This applies equally to the subsequent exemplaryconfigurations of this embodiment as well.

Also, the electro-optic element 23 preferably has a square pillar shape,but it is not necessarily limited to the square pillar shape and it maybe any other shape such as a cylindrical shape.

On two opposing side faces along the vertical direction in the figure ofthe electro-optic element 23, first and second electrodes 25 and 27 areprovided. Note that the first and second electrodes 25 and 27 arearranged such that they are pinching a propagating direction of thelaser light from the laser diode 21 in the electro-optic element 23 fromboth sides and coupling the electric field perpendicularly with respectto the laser light as will be described below.

The electric field detecting device 11 has a signal electrode 29 thatconstitutes the reception electrode 107 of the transceiver 3, and thissignal electrode 29 is connected to the first electrode 25. Also, thesecond electrode 27 facing against the first electrode 25 is connectedto a ground electrode 31, such that it functions as a ground electrodewith respect to the first electrode 25. Note that the ground electrode31 functions as a ground by being connected to a battery of thetransceiver 3 or a large metal, for example, and plays a role ofimproving the coupling of the electric field from the first electrode 25to the electro-optic element 23, but the ground electrode 31 is notabsolutely necessary. This equally applies to the subsequent exemplaryconfigurations of this embodiment as well.

The signal electrode 29 constitutes the reception electrode 107, whichdetects the electric fields induced in and propagated through the livingbody 100, propagates these electric fields to the first electrode 25,and couples them to the electro-optic element 23 through the firstelectrode 25.

The laser light outputted from the laser diode 21 is turned intoparallel beam through a collimating lens 33, and the parallel beam ofthe laser light is injected into the electro-optic element 23 after itspolarization state is adjusted by a first wave plate 35. The laser lightinjected into the electro-optic element 23 is propagated between thefirst and second electrodes 25 and 27, and while this laser light ispropagating, the signal electrode 29 detects the electric field inducedin and propagated through the living body 100 as described above andcouples this electric field to the electro-optic element 23 through thefirst electrode 25. This electric field is formed from the firstelectrode 25 toward the second electrode 27 connected to the groundelectrode 31, and because it is perpendicular to the propagatingdirection of the laser light injected into the electro-optic element 23from the laser diode 21, the birefringence as the optical characteristicof the electro-optic element 23 is changed as described above, and as aresult the polarization of the laser light is changed.

The laser light with the polarization changed by the electric field fromthe first electrode 25 in the electro-optic element 23 in this way isthen injected into the polarizing beam splitter 39 after itspolarization state is adjusted by the second wave plate 37. Thepolarizing beam splitter 39 constitutes an analyzer and is also called apolarizer, which splits the laser light into the P-polarizationcomponent and the S-polarization component and converts them into thelight intensity changes. The P-polarization component and theS-polarization component split from the laser light by the polarizingbeam splitter 39 are respectively collected by the first and secondfocusing lenses 41 a and 41 b and supplied into the first and secondphotodiodes 43 a and 43 b that constitute the photo-electric conversionunit, such that the P-polarization light signal and the S-polarizationlight signal are converted into the respective electric signals andoutputted from the first and second photodiodes 43 a and 43 b.

Note that, in this embodiment, both the P-polarization component and theS-polarization component split by the polarizing beam splitter 39 areconverted into the electric signals and outputted by the first andsecond photodiodes 43 a and 43 b respectively, but it is also possibleto provide only one of the first and second photodiodes 43 a and 43 band only one of the first and second focusing lenses 41 a and 41 b suchthat only one of the P-polarization component and the S-polarizationcomponent is converted into the electric signals and outputted. Thisalso applies to the other exemplary configurations of the electric fielddetecting optical device according to this embodiment.

As described above, the electric signals outputted from the first andsecond photodiodes 43 a and 43 b are applied with the signal processingssuch as the amplification, the noise removal and the waveform shaping atthe signal processing circuit 109 and then supplied to the wearablecomputer 1 through the I/O circuit 101.

Next, FIG. 16 shows a second exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 12 of FIG. 16 differs fromthat of FIG. 15 in that the two non-opposing side faces 23 a and 23 b ofthe electro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections. Therest of the configuration and the operation of the electric fielddetecting optical device 12 are the same as those of FIG. 15.

The electro-optic element 23 has a property that, when the electricfield is applied, it exhibits the phenomenon called inversepiezo-electric effect in which the crystal constituting theelectro-optic element 23 is physically distorted. The polarization ofthe laser light is changed by the distortion due to this inversepiezo-electric effect, but this change is usually small. However, whenthe electric field is changed at a certain frequency, the physicaldistortion of the electro-optic element 23 is also changed at thatfrequency, and when this change resonates with the distance between theopposing faces of the crystal, the effect becomes large and thepolarization change becomes quite large. When such a resonance occurs,the waveform will be distorted to cause the communication error.

For this reason, in the electric field detecting optical device 12 ofFIG. 16, two non-opposing side faces 23 a and 23 b of the electro-opticelement 23 are shaped obliquely in order to prevent such a resonance dueto the inverse piezo-electric effect from occurring. Note that the slopeangle with respect to the propagating direction of the laser light ispreferably 0.5o to 1.0o. By preventing the resonance by shaping the sidefaces 23 a and 23 b of the electro-optic element 23 obliquely in thisway, it is possible to flatten the frequency characteristic, so that itbecomes possible to surely prevent the communication error due to thewaveform distortion.

Next, FIG. 17 shows a third exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 13 of FIG. 17 is similar tothat of FIG. 15 in that it has the laser diode 21 and the electro-opticelement 23 and detects the electric fields by the electro-optic method,but differs from that of FIG. 15 in that, in contrast to the electricfield detecting optical device 11 of FIG. 15 which is a transmissiontype in which the laser light transmits through the electro-opticelement 23, the electric field detecting optical device 13 of FIG. 17 isa reflection type in which a reflection film 51 is provided at an endface on opposite side of an end face of the electro-optic element 23 atwhich the laser light from the laser diode 21 is injected, such that thelaser light propagated through the electro-optic element 23 is reflectedby the reflection film 51 and outputted from the injection end face.

Namely, the electric field detecting optical device 13 of FIG. 17 issimilar to the electric field detecting optical device 11 of FIG. 15 inthat it has a collimating lens 33 for turning the laser light from thelaser diode 21 into the parallel beam, the first and second electrodes25 and 27 provided at two opposing side faces of the electro-opticelement 23, the signal electrode 29 and the ground element 31 connectedto the first and second electrodes 25 and 27 respectively, the first andsecond focusing lenses 41 a and 41 b for collecting the P-polarizationcomponent and the S-polarization component of the laser light, and thefirst and second photodiodes 43 a and 43 b for respectively convertingthe P-polarization light signal and the S-polarization light signalcollected by the first and second focusing lenses 41 a and 41 b intoelectric signals.

In addition to these constituent elements, the electric field detectingoptical device 13 of FIG. 17 has an optical isolator 61 for passing thelaser light injected from the collimating lens 33 toward theelectro-optic element 23, splitting the returning laser light reflectedby the reflection film 51 of the electro-optic element 23 into theP-polarization component and the S-polarization component, andconverting them into the light intensity changes, and a second waveplate 63 for adjusting the polarization state of the laser light, whichare provided between the collimating lens 33 and the electro-opticelement 23, where the optical isolator 61 comprises a first polarizingbeam splitter 53, a first wave plate 55 formed by a _g/2 wave plate, aFaraday element 57, and a second beam splitter 59.

In the optical isolator 61, the first polarizing beam splitter 53 passesthe laser light from the collimating lens 33 while splitting theP-polarization component or the S-polarization component from thereflected light coming from the electro-optic element 23, converting itinto the light intensity change and injecting it into the first focusinglens 41 a. The first wave plate 55 formed by the _g/2 wave plate adjuststhe polarization state of the laser light coming from the collimatinglens 33 by passing through the first polarizing beam splitter 53 and thereflected light coming from the electro-optic element 23. The Faradayelement 57 rotates the polarization plane of the laser light with itspolarization state adjusted by the first wave plate 55 and the reflectedlight coming from the electro-optic element 23. The second polarizingbeam splitter 59 passes the laser light coming from the Faraday element57 to the electro-optic element 23, while splitting the S-polarizationcomponent or the P-polarization component from the reflected lightcoming from the electro-optic element 23, converting it into the lightintensity change and injecting it into the second focusing lens 41 b.

In further detail, the optical isolator 61 passes the laser light comingfrom the collimating lens 33, and the second wave plate 63 adjusts thepolarization state of the laser light and injects it into theelectro-optic element 23. While this injected laser light propagatesthrough the electro-optic element 23 between the first and secondelectrodes 25 and 27, the signal electrode 29 detects the electric fieldinduced in and propagated through the living body 100 and couples thiselectric field to the electro-optic element 23 through the firstelectrode 25. This electric field is formed from the first electrode 25toward the second electrode 27 connected to the ground electrode 31, andbecause it is perpendicular to the propagating direction of the laserlight injected into the electro-optic element 23 from the laser diode21, the birefringence as the optical characteristic of the electro-opticelement 23 is changed, and as a result the polarization of the laserlight is changed.

The laser light with the polarization state changed as a result ofpassing through the electro-optic element 23 with the opticalcharacteristic changed by the electric field then reaches to thereflection film 51 and is reflected by the reflection film 51. Thepolarization state is similarly changed while returning in the oppositedirection through the electro-optic element 23, and the laser lightoutputted from the electro-optic element 23 is injected into the opticalisolator 61, split into the P-polarization component and theS-polarization component and converted into light intensity changes andoutputted by the first and second polarizing beam splitters 53 and 59 ofthe optical isolator 61.

The P-polarization component and the S-polarization component of thelaser light outputted from the first and second polarizing beamsplitters 53 and 59 of the optical isolator 61 in this way are thencollected by the first and second focusing lenses 41 a and 41 b, andinjected into the first and second photodiodes 43 a and 43 b, where theyare converted into electric signals and outputted.

In this exemplary configuration, the laser light passes through theelectro-optic element 23 back and forth by being reflected at thereflection film 51 so that it has a long optical path length for whichit is influenced by the electric field, and therefore the largepolarization change is caused to the laser light and the large signalcan be obtained. Consequently, the sufficient sensitivity can beobtained even by the electro-optic element in a small size, so that itbecomes possible to realize the electric field detecting optical devicein a smaller size at low cost.

Next, FIG. 18 shows a fourth exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 14 of FIG. 18 differs fromthat of FIG. 17 in that the two non-opposing side faces of theelectro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections, so asto prevent the resonance due to the inverse piezo-electric effect of theelectro-optic element 23, flatten the frequency characteristic, andprevent the communication error due to the waveform distortion fromoccurring. The rest of the configuration and the operation of theelectric field detecting optical device 14 are the same as those of FIG.17.

Note that in FIG. 18, only an upper side face of the electro-opticelement 23 is shown to be shaped obliquely, but a side face adjacent toand not opposing this upper side face is actually also shaped obliquely.

Next, FIG. 19 shows a fifth exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 15 of FIG. 19 is similar tothat of FIG. 15 in that it has the laser diode 21 and the electro-opticelement 23 and detects the electric fields by the electro-optic method,but differs from that of FIG. 15 in that, in contrast to the electricfield detecting optical device 11 of FIG. 15 which is a straighttransmission type in which the laser light transmits through theelectro-optic element 23 straight, the electric field detecting opticaldevice 15 of FIG. 19 is a multiple reflection transmission type in whichthe laser light transmits through the electro-optic element 23 whilemaking multiple reflections.

Note that the electro-optic element 23 is basically the same as beforein that it has a sensitivity for the electric field perpendicular to thepropagating direction of the laser light and changes its opticalcharacteristic according to the coupled electric field strengthsimilarly as in the above, but the propagating direction of the laserlight and the direction of the electric field need not be strictlyperpendicular, and it suffices to be nearly perpendicular as shown inFIG. 19, i.e., it may be deviated somewhat from being strictlyperpendicular.

In order to make the multiple reflections of the laser light in theelectro-optic element 23 while coupling the electric field nearlyperpendicularly with respect to the propagating direction of themultiply reflected laser light in this way, the electric field detectingoptical device 15 of FIG. 19 has first and second reflection films 71and 73 provided on two side faces that are opposing to each other alonga direction perpendicular to an opposing direction of the side faces ofthe electro-optic element 23 on which the first and second electrodes 25and 27 are provided, such that the laser light is multiply reflectedbetween these first and second reflection films 71 and 73. Note that therest of the configuration is basically the same as that of FIG. 15.

Then, the laser light from the laser diode 21 is turned into theparallel beam by the collimating lens 33, and after its polarizationstate is adjusted by the first wave plate 35, it is injected into theelectro-optic element 23 from a space between the second reflection film73 and the first electrode 25 toward the first reflection film 71 suchthat it is nearly perpendicular to the electric field between the firstand second electrodes 25 and 27, multiply reflected by repeating theoperation as shown in FIG. 19 in which it is reflected into a directionnearly perpendicular to the electric field similarly by the firstreflection film 71, then it is reflected into a direction nearlyperpendicular to the electric field by the second reflection film 73,and so on, and eventually outputted to the external from a space betweenthe second reflection film 73 and the second electrode 27.

While the laser light is multiply reflected in the electro-optic element23 in this way, the signal electrode 29 detects the electric fieldinduced in and propagated through the living body 100 and couples thiselectric field to the electro-optic element 23 through the firstelectrode 25. This electric field is formed from the first electrode 25toward the second electrode 27 connected to the ground electrode 31, andbecause it is nearly perpendicular to the propagating direction, i.e.,the multiply reflected directions, of the laser light injected into theelectro-optic element 23 from the laser diode 21 and multiply reflectedtherein, the birefringence as the optical characteristic of theelectro-optic element 23 is changed, and as a result the polarization ofthe multiply reflected laser light is changed.

The laser light with the polarization state changed while being multiplyreflected and outputted from the electro-optic element 23 is theninjected into the polarizing beam splitter 39 after its polarizationstate is adjusted by the second wave plate 37. The polarizing beamsplitter 39 splits the laser light from the second wave plate 37 intothe P-polarization component and the S-polarization component andconverts them into the light intensity changes. The P-polarizationcomponent and the S-polarization component split from the laser light bythe polarizing beam splitter 39 are respectively collected by the firstand second focusing lenses 41 a and 41 b and supplied into the first andsecond photodiodes 43 a and 43 b such that the P-polarization lightsignal and the S-polarization light signal are converted into therespective electric signals and outputted from the first and secondphotodiodes 43 a and 43 b.

In this exemplary configuration, the laser light is multiply reflectedwithin the electro-optic element 23 so that it has a long optical pathlength for which it is influenced by the electric field, and thereforethe large polarization change is caused to the laser light and the largesignal can be obtained. Consequently, the sufficient sensitivity can beobtained even by the electro-optic element in a small size, so that itbecomes possible to realize the electric field detecting optical devicein a smaller size at low cost.

Note that, it is also possible to modify this electric field detectingoptical device 15 of FIG. 19 such that the two non-opposing side facesof the electro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections, so asto prevent the resonance due to the inverse piezo-electric effect of theelectro-optic element 23, flatten the frequency characteristic, andprevent the communication error due to the waveform distortion fromoccurring, similarly as in the cases of FIG. 16 and FIG. 18.

As described, according to this embodiment, the electric field inducedin and propagated through the electric field propagating medium iscoupled to the electro-optic element through the first electrode, theparallel beam is injected into this electro-optic element, and it issplit into the P-polarization component and the S-polarizationcomponent, converted into the light intensity changes by the analyzer,and at least one of the P-polarization component and the S-polarizationcomponent is converted into the electric signals and outputted, so thatby applying this embodiment to the transceiver for the wearablecomputer, for example, it becomes possible to properly carry out thecommunications among the wearable computers, which do not require anycable lines, which are free from the cross-talking with the other radiosystems, and which do not depend on the Earth ground.

Also, according to this embodiment, the electric field induced in andpropagated through the electric field propagating medium is coupled tothe electro-optic element through the first electrode, the parallel beamis injected into this electro-optic element to make the reflection orthe multiple reflections, and the parallel beam outputted from theelectro-optic element is split into the P-polarization component and theS-polarization component, converted into the light intensity changes,and at least one of the P-polarization component and the S-polarizationcomponent is converted into the electric signals and outputted, so thatby applying this embodiment to the transceiver for the wearablecomputer, for example, it becomes possible to properly carry out thecommunications among the wearable computers, which do not require anycable lines, which are free from the cross-talking with the other radiosystems, and which do not depend on the Earth ground.

In addition, the parallel beam is reflected or multiply reflected in theelectro-optic element, so that it has a long optical path length forwhich it is influenced by the electric field, and therefore the largepolarization change is caused to the laser light and the large signalcan be obtained. Consequently, the sufficient sensitivity can beobtained even by the electro-optic element in a small size, so that itbecomes possible to realize the electric field detecting optical devicein a smaller size at low cost.

Referring now to FIG. 20 to FIG. 25, the fifth embodiment of the presentinvention related to the electric field detecting optical device will bedescribed in detail.

FIG. 20 shows a first exemplary configuration of the electric fielddetecting optical device according to this embodiment.

The electric field detecting optical device 11′ of FIG. 20 is to be usedas the electric field detecting optical unit 110 in the transceiver 3 ofthe first to third embodiments described above, in the case of puttingthe wearable computer 1 on the living body 100 which is an electricfield propagating medium and enabling the data communications with theother wearable computers and data communication devices.

The electric field detecting optical device 11′ of FIG. 20 detects theelectric fields by the electro-optic method using laser lights andelectro-optic crystals, and has a laser diode 21 constituting a laserlight source and an electro-optic element 23 in a form of anelectro-optic crystal. Note that the electro-optic element 23 of thisembodiment is a longitudinal type electro-optic element which issensitive only to electric fields coupled in a direction parallel to apropagating direction of the laser light from the laser diode 21, wherethe optical characteristic, i.e., the birefringence, is changed by theelectric field strength and the polarization of the laser light ischanged by the change of the birefringence, as indicated in FIG. 20.

Note also that the laser light outputted from the laser diode 21 is usedin this embodiment, but it is not necessarily limited to the laser lightand it suffices to be a single wavelength light, so that it is alsopossible to use the light outputted from a light emitting diode (LED),for example. This applies equally to the subsequent exemplaryconfigurations of this embodiment as well.

Also, the electro-optic element 23 preferably has a square pillar shape,but it is not necessarily limited to the square pillar shape and it maybe any other shape such as a cylindrical shape.

The laser light from the laser diode 21 is turned into the parallel beamby the collimating lens 33, passed through the optical isolator 61formed by the first polarizing beam splitter 53, the first wave plate 55formed by the _g/2 wave plate, the Faraday element 57, and the secondpolarizing beam splitter 59, and injected into the electro-optic element23 after its polarization state is adjusted by the second wave plate 63.Note that the polarizing beam splitters 53 and 59 constitute theanalyzer and are also called polarizers.

On an end face of the electro-optic element 23 opposite to the end facefrom which the laser light is injected, the first electrode 25 formed bya metallic mirror is provided such that the laser light injected intothe electro-optic element 23 is reflected to a direction opposite tothat of the injection direction by this first electrode 25. Also, thefirst electrode 25 is connected to the signal electrode 29 thatconstitutes the reception electrode 107, and this signal electrode 29detects the electric field induced in and propagated through the livingbody 100 and this electric field is coupled to the electro-optic element23 through the first electrode 25.

In the optical isolator 61, the first polarizing beam splitter 53 passesthe laser light from the collimating lens 33 while splitting theP-polarization component or the S-polarization component from thereflected light coming from the electro-optic element 23, converting itinto the light intensity change and injecting it into the first focusinglens 41 a. The first wave plate 55 formed by the _g/2 wave plate adjuststhe polarization state of the laser light coming from the collimatinglens 33 by passing through the first polarizing beam splitter 53 and thereflected light coming from the electro-optic element 23. The Faradayelement 57 rotates the polarization plane of the laser light with itspolarization state adjusted by the first wave plate 55 and the reflectedlight coming from the electro-optic element 23. The second polarizingbeam splitter 59 passes the laser light coming from the Faraday element57 to the electro-optic element 23, while splitting the S-polarizationcomponent or the P-polarization component from the reflected lightcoming from the electro-optic element 23, converting it into the lightintensity change and injecting it into the second focusing lens 41 b.

In further detail, the optical isolator 61 passes the laser light comingfrom the collimating lens 33, and the second wave plate 63 adjusts thepolarization state of the laser light and injects it into theelectro-optic element 23. While this injected laser light propagatesthrough the electro-optic element 23, the signal electrode 29 detectsthe electric field induced in and propagated through the living body 100and couples this electric field to the electro-optic element 23 throughthe first electrode 25. Because this electric field is parallel to thepropagating direction of the laser light injected into the electro-opticelement 23 from the laser diode 21, the birefringence as the opticalcharacteristic of the electro-optic element 23 is changed, and as aresult the polarization of the laser light is changed.

The laser light with the polarization state changed as a result ofpassing through the electro-optic element 23 with the opticalcharacteristic changed by the electric field is then reflected by thereflection film (the first electrode 25). The polarization state issimilarly changed while returning in the opposite direction through theelectro-optic element 23, and the laser light is outputted in adirection opposite to the injection direction from the electro-opticelement 23. This laser light outputted from the electro-optic element 23is injected into the optical isolator 61, split into the P-polarizationcomponent and the S-polarization component and converted into lightintensity changes and outputted by the first and second polarizing beamsplitters 53 and 59 of the optical isolator 61.

The P-polarization component and the S-polarization component of thelaser light outputted from the first and second polarizing beamsplitters 53 and 59 of the optical isolator 61 in this way are thencollected by the first and second focusing lenses 41 a and 41 b, andinjected into the first and second photodiodes 43 a and 43 b, where theyare converted into electric signals and outputted.

Note that, in this embodiment, both the P-polarization component and theS-polarization component split by the polarizing beam splitters 53 and59 are converted into the electric signals and outputted by the firstand second photodiodes 43 a and 43 b respectively, but it is alsopossible to provide only one of the first and second photodiodes 43 aand 43 b and only one of the first and second focusing lenses 41 a and41 b such that only one of the P-polarization component and theS-polarization component is converted into the electric signals andoutputted. This also applies to the other exemplary configurations ofthe electric field detecting optical device according to thisembodiment.

As described above, the electric signals outputted from the first andsecond photodiodes 43 a and 43 b are applied with the signal processingssuch as the amplification, the noise removal and the waveform shaping atthe signal processing circuit 109 and then supplied to the wearablecomputer 1 through the I/O circuit 101.

In this exemplary configuration, the laser light passes through theelectro-optic element 23 back and forth by being reflected at thereflection film (the first electrode 25) so that it has a long opticalpath length for which it is influenced by the electric field, andtherefore the large polarization change is caused to the laser light andthe large signal can be obtained. Consequently, the sufficientsensitivity can be obtained even by the electro-optic element in a smallsize, so that it becomes possible to realize the electric fielddetecting optical device in a smaller size at low cost.

Next, FIG. 21 shows a second exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 12′ of FIG. 21 differs fromthat of FIG. 20 in that the two non-opposing side faces 23 a and 23 b ofthe electro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections. Therest of the configuration and the operation of the electric fielddetecting optical device 12′ are the same as those of FIG. 20.

The electro-optic element 23 has a property that, when the electricfield is applied, it exhibits the phenomenon called inversepiezo-electric effect in which the crystal constituting theelectro-optic element 23 is physically distorted. The polarization ofthe laser light is changed by the distortion due to this inversepiezo-electric effect, but this change is usually small. However, whenthe electric field is changed at a certain frequency, the physicaldistortion of the electro-optic element 23 is also changed at thatfrequency, and when this change resonates with the distance between theopposing faces of the crystal, the effect becomes large and thepolarization change becomes quite large. When such a resonance occurs,the waveform will be distorted to cause the communication error.

For this reason, in the electric field detecting optical device 12′ ofFIG. 21, two non-opposing side faces 23 a and 23 b of the electro-opticelement 23 are shaped obliquely in order to prevent such a resonance dueto the inverse piezo-electric effect from occurring. Note that the slopeangle with respect to the propagating direction of the laser light ispreferably 0.5o to 1.0o. By preventing the resonance by shaping the sidefaces 23 a and 23 b of the electro-optic element 23 obliquely in thisway, it is possible to flatten the frequency characteristic, so that itbecomes possible to surely prevent the communication error due to thewaveform distortion.

Next, FIG. 22 shows a third exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 13′ of FIG. 22 differs fromthat of FIG. 20 in that the second electrode 27 is provided on one sideface of the electro-optic element 23, and this second electrode 27 isconnected to the ground electrode 31 such that it functions as theground electrode with respect to the first electrode 25. The rest of theconfiguration and the operation of the electric field detecting opticaldevice 13′ are the same as those of FIG. 20.

The second electrode 27 functions as a ground by being connected to abattery of the transceiver 3 or a large metal, for example, through theground electrode 31, and plays a role of improving the coupling of theelectric field from the first electrode 25 to the electro-optic element23.

Next, FIG. 23 shows a fourth exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 14′ of FIG. 23 differs fromthat of FIG. 20 in that a transparent second electrode 27 a formed byITO (Indium Tin Oxide) for example is provided between the electro-opticelement 23 and the second wave plate 63, and this second electrode 27 ais connected to the ground electrode 31 such that it functions as theground electrode with respect to the first electrode 25. The rest of theconfiguration and the operation of the electric field detecting opticaldevice 13′ are the same as those of FIG. 20.

The second electrode 27 a functions as a ground by being connected to abattery of the transceiver 3 or a large metal, for example, through theground electrode 31, and plays a role of improving the coupling of theelectric field from the first electrode 25 to the electro-optic element23, similarly as in the case of FIG. 22.

Note that the second electrode 27 a is formed to be transparent so thatit passes the laser light from the laser diode 21 and the reflectedlight from the electro-optic element 23 as they are.

Next, FIG. 24 shows a fifth exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 16 of FIG. 24 is similar tothat of FIG. 20 in that it has the laser diode 21 and the electro-opticelement 23 and detects the electric fields by the electro-optic method,but differs from that of FIG. 20 in that, in contrast to the electricfield detecting optical device 11′ of FIG. 20 which is a reflection typein which the laser light is reflected by a reflection film (the firstelectrode 25) provided at the other end face of the electro-opticelement 23 so as to pass the electro-optic element 23 back and forth,the electric field detecting optical device 16 of FIG. 24 is atransmission type in which the laser light from the laser diode 21transmits through the electro-optic element 23.

Note that the electro-optic element 23 is sensitive only to electricfields coupled in a direction parallel to a propagating direction of thelaser light, and changes its optical characteristic according to thecoupled electric field strength similarly as in the above.

In the electric field detecting optical device 16 of FIG. 24, the laserlight from the laser diode 21 is turned into parallel beam through thecollimating lens 33, and injected into the electro-optic element 23after its polarization state is adjusted by the first wave plate 35. Inthis case, in order to generate the electric field parallel to the laserlight in the electro-optic element 23, transparent first and secondelectrodes 25 a and 27 b formed by ITO for example are provided at twoend faces of the electro-optic element 23, i.e., the injection end faceand the output end face which is an end face opposing the injection endface, such that the laser light from the laser diode 21 is injected intothe electro-optic element 23 through the transparent first electrode 25a.

The first electrode 25 a and the second electrode 27 b are connected tothe signal electrode 29 and the ground electrode 31 respectively. Thesignal electrode 29 constitutes the reception electrode 107, whichdetects the electric fields induced in and propagated through the livingbody 100, propagates these electric fields to the first electrode 25 a,and couples them to the electro-optic element 23 through the firstelectrode 25 a. The second electrode 27 b functions as a ground by beingconnected to a battery of the transceiver 3 or a large metal, forexample, through the ground electrode 31 and plays a role of improvingthe coupling of the electric field from the first electrode 25 a to theelectro-optic element 23, but the second electrode 27 b and the groundelectrode 31 are not absolutely necessary.

Note that, in the configuration described above, the first electrode 25a and the second electrode 27 b are arranged such that the firstelectrode 25 a provided on the injection end face of the electro-opticelement 23 is connected to the signal electrode 29 so that the electricfield is coupled to the electro-optic element 23 from the signalelectrode 29 through the first electrode 25 a, while the secondelectrode 27 b provided on the output end face is connected to theground electrode 31, but the first electrode 25 a and the secondelectrode 27 b may be interchanged. Namely, it is also possible to use aconfiguration in which the second electrode 27 b is connected to thesignal electrode 29 so that the electric field is coupled to theelectro-optic element 23 from the signal electrode 29 through the secondelectrode 27 b, while the first electrode 25 a is connected to theground electrode 31.

The laser light injected into the electro-optic element 23 is propagatedtoward the second electrode 27 b on the output end face, and while thislaser light is propagating, the signal electrode 29 detects the electricfield induced in and propagated through the living body 100 as describedabove and couples this electric field to the electro-optic element 23through the first electrode 25 a. This electric field is formed from thefirst electrode 25 a toward the second electrode 27 b connected to theground electrode 31, and because it is parallel to the propagatingdirection of the laser light injected into the electro-optic element 23from the laser diode 21, the birefringence as the optical characteristicof the electro-optic element 23 is changed as described above, and as aresult the polarization of the laser light is changed.

The laser light with the polarization changed by the electric field fromthe first electrode 25 a in the electro-optic element 23 in this way isthen outputted from the electro-optic element 23, passed through thetransparent second electrode 27 b, and injected into the polarizing beamsplitter 39 that constitutes an analyzer after its polarization state isadjusted by the second wave plate 37.

The polarizing beam splitter 39 splits the laser light into theP-polarization component and the S-polarization component and convertsthem into the light intensity changes. The P-polarization component andthe S-polarization component split from the laser light by thepolarizing beam splitter 39 are respectively collected by the first andsecond focusing lenses 41 a and 41 b and supplied into the first andsecond photodiodes 43 a and 43 b that constitute the photo-electricconversion unit, such that the P-polarization light signal and theS-polarization light signal are converted into the respective electricsignals and outputted from the first and second photodiodes 43 a and 43b.

As described above, the electric signals outputted from the first andsecond photodiodes 43 a and 43 b are applied with the signal processingssuch as the amplification, the noise removal and the waveform shaping atthe signal processing circuit 109 and then supplied to the wearablecomputer 1 through the I/O circuit 101.

Note that, it is also possible to modify this electric field detectingoptical device 16 of FIG. 24 such that the two non-opposing side facesof the electro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections, so asto prevent the resonance due to the inverse piezo-electric effect of theelectro-optic element 23, flatten the frequency characteristic, andprevent the communication error due to the waveform distortion fromoccurring, similarly as in the case of FIG. 21.

Next, FIG. 25 shows a sixth exemplary configuration of the electricfield detecting optical device according to this embodiment.

The electric field detecting optical device 15′ of FIG. 25 is similar tothat of FIG. 24 in that it has the laser diode 21 and the electro-opticelement 23 and detects the electric fields by the electro-optic method,but differs from that of FIG. 24 in that, in contrast to the electricfield detecting optical device 16 of FIG. 24 which is a straighttransmission type in which the laser light transmits through theelectro-optic element 23 straight, the electric field detecting opticaldevice 15′ of FIG. 25 is a multiple reflection transmission type inwhich the laser light transmits through the electro-optic element 23while making multiple reflections.

Note that the electro-optic element 23 is basically the same as beforein that it has a sensitivity for the electric field parallel to thepropagating direction of the laser light and changes its opticalcharacteristic according to the coupled electric field strengthsimilarly as in the above, but the propagating direction of the laserlight and the direction of the electric field need not be strictlyparallel, and it suffices to be nearly parallel as shown in FIG. 25,i.e., it may be deviated somewhat from being strictly parallel.

In order to make the multiple reflections of the laser light in theelectro-optic element 23 while coupling the electric field nearlyparallel with respect to the propagating direction of the multiplyreflected laser light in this way, the electric field detecting opticaldevice 15′ of FIG. 25 has the first and second 25 and 27 formed bymetallic mirrors provided on the injection end face and the other endface opposing the injection end face, respectively, such that the laserlight injected from the laser diode 21 is multiply reflected betweenthese first and second electrodes 25 and 27.

Also, the first and second electrodes 25 and 27 are connected to thesignal electrode 29 and the ground electrode 31 respectively, similarlyas in the above. Note that, in the configuration shown in FIG. 25, thesecond electrode 27 is provided on the end face from which the laserlight is injected, and the first electrode 25 is provided on the otherend face opposing the injection end face, but they can be interchanged.Also, the output end face of the laser light is set to be on the sameside as the injection end face, but they may be set on different sides.

In the configuration of FIG. 25, the laser light from the laser diode 21is turned into the parallel beam by the collimating lens 33, and afterits polarization state is adjusted by the first wave plate 35, it isinjected into the electro-optic element 23. In this injection, the laserlight is injected into the electro-optic element 23 from a portion nearone edge of the injection end face on which the second electrode 27 isprovided, for example, such that it is nearly parallel to the electricfield between the first and second electrodes 25 and 27, multiplyreflected by repeating the operation as shown in FIG. 25 in which it isreflected into a direction nearly parallel to the electric fieldsimilarly by the first electrode 25, then it is reflected into adirection nearly parallel to the electric field by the second electrode27, and so on, and eventually outputted to the external from a portionnear another edge of the injection end face on which the secondelectrode 27 is provided.

While the laser light is multiply reflected in the electro-optic element23 in this way, the signal electrode 29 detects the electric fieldinduced in and propagated through the living body 100 and couples thiselectric field to the electro-optic element 23 through the firstelectrode 25. This electric field is formed from the first electrode 25toward the second electrode 27 connected to the ground electrode 31, andbecause it is nearly parallel to the propagating direction, i.e., themultiply reflected directions, of the laser light injected into theelectro-optic element 23 from the laser diode 21 and multiply reflectedtherein, the birefringence as the optical characteristic of theelectro-optic element 23 is changed, and as a result the polarization ofthe multiply reflected laser light is changed.

The laser light with the polarization state changed while being multiplyreflected and outputted from the electro-optic element 23 is theninjected into the polarizing beam splitter 39 that constitutes ananalyzer after its polarization state is adjusted by the second waveplate 37. The polarizing beam splitter 39 splits the laser light fromthe second wave plate 37 into the P-polarization component and theS-polarization component and converts them into the light intensitychanges. The P-polarization component and the S-polarization componentsplit from the laser light by the polarizing beam splitter 39 arerespectively collected by the first and second focusing lenses 41 a and41 b and supplied into the first and second photodiodes 43 a and 43 bsuch that the P-polarization light signal and the S-polarization lightsignal are converted into the respective electric signals and outputtedfrom the first and second photodiodes 43 a and 43 b.

In this exemplary configuration, the laser light is multiply reflectedwithin the electro-optic element 23 so that it has a long optical pathlength for which it is influenced by the electric field, and thereforethe large polarization change is caused to the laser light and the largesignal can be obtained. Consequently, the sufficient sensitivity can beobtained even by the electro-optic element in a small size, so that itbecomes possible to realize the electric field detecting optical devicein a smaller size at low cost.

Note that, it is also possible to modify this electric field detectingoptical device 15′ of FIG. 25 such that the two non-opposing side facesof the electro-optic element 23 are shaped obliquely with respect to thepropagating direction of the laser light to form slope sections, so asto prevent the resonance due to the inverse piezo-electric effect of theelectro-optic element 23, flatten the frequency characteristic, andprevent the communication error due to the waveform distortion fromoccurring, similarly as in the case of FIG. 21.

As described, according to this embodiment, the electric field inducedin and propagated through the electric field propagating medium iscoupled to the electro-optic element through the first electrode, theparallel beam is injected into this electro-optic element to make thereflection or the multiple reflections, and the parallel beam outputtedfrom the electro-optic element is split into the P-polarizationcomponent and the S-polarization component, converted into the lightintensity changes, and at least one of the P-polarization component andthe S-polarization component is converted into the electric signals andoutputted by the optical isolator, so that by applying this embodimentto the transceiver for the wearable computer, for example, it becomespossible to properly carry out the communications among the wearablecomputers, which do not require any cable lines, which are free from thecross-talking with the other radio systems, and which do not depend onthe Earth ground.

In addition, the parallel beam is reflected or multiply reflected in theelectro-optic element, so that it has a long optical path length forwhich it is influenced by the electric field, and therefore the largepolarization change is caused to the laser light and the large signalcan be obtained. Consequently, the sufficient sensitivity can beobtained even by the electro-optic element in a small size, so that itbecomes possible to realize the electric field detecting optical devicein a smaller size at low cost.

Also, according to this embodiment, the electric field induced in andpropagated through the electric field propagating medium is coupled tothe electro-optic element through the first electrode, the parallel beamis injected into and passed through this electro-optic element, and theparallel beam outputted from this electro-optic element is split intothe P-polarization component and the S-polarization component, convertedinto the light intensity changes by the analyzer, and at least one ofthe P-polarization component and the S-polarization component isconverted into the electric signals and outputted, so that by applyingthis embodiment to the transceiver for the wearable computer, forexample, it becomes possible to properly carry out the communicationsamong the wearable computers, which do not require any cable lines,which are free from the cross-talking with the other radio systems, andwhich do not depend on the Earth ground.

Also, according to this embodiment, the two non-opposing side faces ofthe electro-optic element are shaped obliquely with respect to thepropagating direction of the laser light, so that it is possible tosurely prevent the resonance due to the inverse piezo-electric effect ofthe electro-optic element, flatten the frequency characteristic, andprevent the communication error due to the waveform distortion fromoccurring.

Referring now to FIG. 26 to FIG. 28, the sixth embodiment of the presentinvention related to the photodetection circuit will be described indetail.

FIG. 26 shows a first exemplary configuration of the photodetectioncircuit according to this embodiment.

The photodetection circuit of FIG. 26 is to be used as a unit fordetecting the laser light that is split and outputted as theP-polarization component and the S-polarization component from theelectric field detection optical unit 110 of the transceiver 3 that isused for the data communications among the wearable computers asdescribed above, for example, and converting them into the electricsignals. This photodetection circuit of FIG. 26 has first and secondphotodiodes 81 and 82 as the first and second photo-electric conversionunits for detecting the laser light that is outputted by being splitinto the P-polarization component and the S-polarization componentoutputted from the electric field detecting optical unit and convertingthem into the electric signals.

The first and second photodiodes 81 and 82 have their cathodes connectedto first and second constant voltage sources 75 and 76 respectively, andtheir anodes grounded through a fixed resistor 77 and a variableresistor 78 respectively to apply the inverse bias to the first andsecond photodiodes 81 and 82, such that when the lights are injectedinto the first and second photodiodes 81 and 82, the currents will begenerated from the first and second photodiodes 81 and 82 and thesecurrents will flow through the fixed resistor 77 and the variableresistor 78 to cause the voltage droppings.

Also, a contact point between the first photodiode 81 and the fixedresistor 77 and a contact point between the second photodiode 82 and thevariable resistor 78 are connected to inputs of a differential amplifier89, such that the voltages generated as a result of the voltagedroppings caused at the fixed resistor 77 and the variable resistor 78by the currents from the first and second photodiodes 81 and 82 will beentered into the differential amplifier 89 respectively.

In the photodetection circuit in the above described configuration, whenthe first and second photodiodes 81 and 82 detect the laser lights inthe opposite phases in forms of the P-polarization component and theS-polarization component from the electric field detecting optical unitrespectively, the currents according to the intensity changes of thelaser lights are generated, and these currents are flown through thefixed resistor 77 and the variable resistor 78 respectively to cause thevoltage droppings. The voltages generated at the fixed resistor 77 andthe variable resistor 78 are applied to a non-inverted input and aninverted input of the differential amplifier 89 respectively, to bedifferentially amplified by the differential amplifier 89.

In the differential amplification at the differential amplifier 89, theintensity changes of the laser lights entered into the first and secondphotodiodes 81 and 82 have opposite phases, so that they are doubled incorrespondence to a difference between the opposite phases at thedifferential amplifier 89 to output the normal output signals. If noisesare mixed into the laser lights themselves, such noises will normallyhave the same phase and the same level, so that they will be cancelledand removed at the differential amplifier 89 and not be outputted fromthe differential amplifier 89.

However, as described above, the noises mixed into the output currentsof the photodiodes through the metallic casings, for example, of thefirst and second photodiodes 81 and 82 are mixed at different noiselevels in the first and second photodiodes 81 and 82 depending on thepositional relationships or the like between the noise sources and thefirst and second photodiodes 81 and 82, so that they cannot be removedin their original forms even by the differential amplifier 89 and willbe outputted as they are from the differential amplifier 89.

For this reason, in the exemplary configuration of FIG. 26, when theoutput currents of the first and second photodiodes 81 and 82 aredeviated from the nominal current values that would have resultedwithout the influence of the noises because of the noises mixed from themetallic casings or the like of the photodiodes such that the resultingvoltages generated by the fixed resistor 77 and the variable resistor 78are also deviated from the nominal voltage values, the deviated voltagesare reduced or cancelled by adjusting the resistance value of thevariable resistor 78, such that the voltages generated at the fixedresistor 77 and the variable resistor 78 are corrected to the nominalvoltage values without the influence of the noises and then entered intothe differential amplifier 89, so as to remove the noises at differentlevels that are mixed from the metallic casings or the like of the firstand second photodiodes 81 and 82, for example.

Next, FIG. 27 shows a second exemplary configuration of thephotodetection circuit according to this embodiment.

The photodetection circuit of FIG. 27 differs from that of FIG. 26 inthat the voltages to be entered into the differential amplifier 89 areadjusted by using a variable gain amplifier, instead of adjusting thevoltages to be entered into the differential amplifier 89 by using thevariable resistor 78. In the configuration of FIG. 27, a fixed resistor79 is used instead of the variable resistor 78 used in the configurationof FIG. 26, the voltage of the fixed resistor 77 is amplified by a fixedgain amplifier 83 and entered into the differential amplifier 89 whilethe voltage of the fixed resistor 79 is amplified by a variable gainamplifier 84 and entered into the differential amplifier 89, and thegain of this variable gain amplifier 84 is adjusted by a gain controlcircuit 85. The rest of the configuration and the operation are the sameas those of FIG. 26.

Using this configuration, when the noises at different levels are mixedfrom the metallic casings or the like of the first and secondphotodiodes 81 and 82 into the output currents of the photodiodes suchthat the resulting voltages generated at the fixed resistors 77 and 79are deviated from the nominal voltage values as described above, thedeviated voltages are reduced or cancelled by adjusting the gain of thevariable gain amplifier 84, such that the voltages entered into thedifferential amplifier 89 are corrected to the nominal voltage valueswithout the influence of the noises, so as to remove the noises atdifferent levels that are mixed from the metallic casings or the like ofthe first and second photodiodes 81 and 82, for example.

In the overall operation, when the first and second photodiodes 81 and82 detect the laser lights in the opposite phases in forms of theP-polarization component and the S-polarization component from theelectric field detecting optical unit respectively, the currentsaccording to the intensity changes of these laser lights are generated,and these currents are flown through the fixed resistors 77 and 79respectively to cause the voltage droppings. Among the voltagesgenerated at the fixed resistors 77 and 79, the voltage of the fixedresistor 77 is amplified by the fixed gain amplifier 83 and entered intothe differential amplifier 89, and the voltage of the fixed resistor 79is amplified by the variable gain amplifier 84 and entered into thedifferential amplifier 89. Here, the laser lights have opposite phases,so that they are doubled and outputted from the differential amplifier89, while the noises mixed into the laser lights have the same phase andthe same level so that they will be cancelled and removed at thedifferential amplifier 89.

Also, when the noises at different levels are mixed from the metalliccasings or the like of the photodiodes 81 and 82 into the outputcurrents of the photodiodes such that the voltages generated by thefixed resistors 77 and 79 are deviated from the nominal voltage valuesdue to the influence of the noises, the voltages due to the noises areremoved or cancelled by adjusting the gain of the variable gainamplifier 84 in correspondence to the deviated voltages at the gaincontrol circuit 85, such that the voltages without the influence of thenoises will be entered into the differential amplifier 89.

Next, FIG. 28 shows a third exemplary configuration of thephotodetection circuit according to this embodiment.

The photodetection circuit of FIG. 28 differs from that of FIG. 26 inthat the fixed resistor 79 is used instead of the variable resistor 78used in the configuration of FIG. 26 and a variable voltage source 76 ais used instead of the second constant voltage source 76 used in theconfiguration of FIG. 26, and the conversion efficiency of thephotodiode is changed by varying the voltage of this variable voltagesource 76 a so as to adjust the voltage generated at the fixed resistor79 as a result. The rest of the configuration and the operation are thesame as those of FIG. 26.

Namely, as described with reference to FIG. 26, when the noises atdifferent levels are mixed from the metallic casings or the like of thefirst and second photodiodes 81 and 82 into the output currents of thephotodiodes such that the resulting voltages generated at the fixedresistors 77 and 79 are deviated from the nominal voltage values, thedeviated voltages are reduced or cancelled by adjusting the voltage ofthe variable voltage source 76 a, such that the voltages entered intothe differential amplifier 89 are corrected to the nominal voltagevalues without the influence of the noises, so as to remove the noisesat different levels that are mixed from the metallic casings or the likeof the first and second photodiodes 81 and 82, for example.

Note that the above described exemplary configurations are directed tothe cases of providing the variable resistor 78, the variable gainamplifier 84 and the gain control circuit 85, or the variable voltagesource 76 a on the second photodiode 82 side among the first and secondphotodiodes 81 and 82, but this embodiment is not necessarily limited tothese cases, and it is also possible to provide them on the firstphotodiode 81 side or on both sides. In principle, it suffices toprovide them at least on either one side.

As described, according to this embodiment, the electric signalsobtained by the photo-electric conversion at the first and secondphoto-electric conversion units are converted into voltage signals andentered into a differential amplifier, and the voltage signalscorresponding to the normal input lights are doubled and normallyoutputted from the differential amplifier, while the voltagescorresponding to the noises of the same phase and the same level thatare mixed into the input lights are removed by the differentialamplifier, and the noises at different levels that are mixed into thecurrent signals or the voltage signals can be surely removed byadjusting the adjustment unit such as a variable resistor, a variablegain amplifier or a variable voltage source as much as the voltagesdeviated from the nominal voltage values in correspondence to thenoises.

It is also to be noted that, besides those already mentioned above, manymodifications and variations of the above embodiments may be madewithout departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

1. A transceiver for inducing electric fields based on data to betransmitted in an electric field propagating medium and carrying outtransmission and reception of data by using induced electric fields,comprising: a transmission electrode configured to induce the electricfields based on the data to be transmitted in the electric fieldpropagating medium; a transmission circuit configured to supplytransmission data for causing the transmission electrode to induce theelectric fields based on the data to be transmitted in the electricfield propagating medium, to the transmission electrode; a receptionelectrode configured to receive electric fields induced in andpropagated through the electric field propagating medium; an electricfield detection unit configured to detect received electric fields asreceived by the reception electrode, and convert the received electricfields into electric signals by causing a resonance in an electro-opticelement by using the received electric fields; a modulation circuitconfigured to modulate the transmission data by using resonantfrequencies of the electro-optic element as modulation frequencies, andsupply modulated transmission data to the transmission circuit; and ademodulation circuit configured to demodulate the electric signals fromthe electric field detection unit.
 2. The transceiver of claim 1,wherein the modulation circuit modulates the transmission data by usingarbitrary two resonant frequencies of the electro-optic element asdigital modulation frequencies corresponding to high level and low levelof the transmission data.